Some transmission type image display apparatuses such as liquid crystal display apparatuses and sign boards use a direct surface light source device as a backlight. In recent years, direct surface light source devices having a plurality of light emitting elements as the light source are used. In such surface light source devices, a light flux controlling member for controlling the distribution of the light emitted from the light emitting element is disposed over the light emitting element (see, for example, PTL 1).
FIG. 1 is a sectional view of surface light source device 10 disclosed in PTL 1. As illustrated in FIG. 1, surface light source device 10 includes light-emitting device 20, and light diffusion member 30 disposed on light-emitting device 20 with an air layer therebetween. In addition, light-emitting device 20 includes light emitting element 40, and a lens (light flux controlling member) 50 disposed on light emitting element 40. Lens 50 is a condenser lens including incidence surface 51 disposed on light emitting element 40 side, reflecting surface 52 disposed to surround incidence surface 51 and configured to reflect light incident on incidence surface 51, and emission surface 53 configured to emit light incident on incidence surface 51 and light incident on incidence surface 51 which is reflected by reflecting surface 52. In addition, in surface light source device 10 disclosed in PTL 1, a light diffusion treatment is performed on incidence surface 51, reflecting surface 52 or emission surface 53. A part of light emitted from light emitting element 40 which is incident on incidence surface 51 is reflected by reflecting surface 52 and then emitted from emission surface 53 to the outside. In addition, the other part of light emitted from light emitting element 40 which is incident on incidence surface 51 is emitted from emission surface 53 to the outside without being reflected by reflecting surface 52. In lens 50 of surface light source device 10 disclosed in PTL 1, incidence surface 51, reflecting surface 52 or emission surface 53 is subjected to a light diffusion treatment to prevent color unevenness in light diffusion member 30.